The present invention relates generally to medical electronic apparatus and electrical switching devices, and more particularly to such a device especially suitable as an electrosurgical switching handpiece.
Various types of electrosurgical tools have been suggested and utilized in the medical field for a considerable period of time. Typically, in electrosurgery, a suitable electrical generator provides a high frequency or radio-frequency (RF) signal which is transmitted to a small surgical electrode having a thin knife-like tip to be applied to a patient. The patient sits or lies on a patient plate and is grounded thereto, with the plate being connected by a further conductor back to the generator. The relatively extremely small area of contact by the electrode with the patient provides an intense current in a highly localized area, producing a cutting action. The current passes through the patient's body to the patient plate where the area of contact is so great that no burning effect occurs to the patient.
For cutting purposes, the generator is activated to produce a continuous signal, typically a sinewave signal. However the same instrument may be used to apply to the wound after cutting in order to produce coagulation. For this purpose the generator may be selectively activated to produce a pulsing signal which produces the desired results. Switching means are available for the operator to selectively control an activating means for causing the generator to produce the desired type of current.
Suitable control switches may be mounted on the instrument panel of the generator to be operated by an assistant. This is generally considered to be unsatisfactory because of the delay involved in transmitting instructions. In other designs, foot operated switches are provided which may be controlled by the surgeon. However, this interferes with his mobility because he must stand in one place or move the foot switches about on the floor.
Various hand operated switching mechanisms for the dual purpose of cutting and coagulating tissue by the selective application of high frequency current of a selected type and power have become well known in the art. Such prior art devices include:
U.S. Pat. No. 3,801,766 to Morrison, Jr. discloses a hand-held electrical switching device for an electrosurgical instrument including a rectangularly shaped printed circuit board including three spaced apart electrical contacts. A spring contact member is disposed in electrical conducting engagement with the center contact and includes oppositely positioned contacts, each of which is adapted to be selectively engaged to one of the other contacts by means of a hand-activated rocker button. The Morrison patent is assigned to Valleylab, and while not described in this present patent, Valleylab markets a similar electrosurgical device which includes a sleeve member which is heat-shrunk over the printed circuit board to seal the circuit board from fluids. Such heat sealing requires the use of special equipment which is costly.
U.S. Pat. No. 3,911,241 to Jarrard shows an electrosurgical instrument including a switch with a pair of spaced contacts encased in a flexible housing. The space between the contacts allows actuation of the switch by manually squeezing the housing. More than one pair of spaced contacts may be incorporated in the housing. This reference discloses the use of a heat-shrinkable flexible covering to establish an environmental seal about the conductive elements.
U.S. Pat. No. 4,034,761 to Preter shows a hand-held electrosurgical switching assembly in which the switching member is mounted in the electrode handle for selectively moving one of the bowed portions of the resilient conductive member into contact with a wire wrap contact for actuation of the electrode blade in a desired operative mode.
U.S. Pat. Nos. 4,112,950 to Pike; 4,170,234 to Graham; and 4,202,337 to Hren illustrate additional hand-actuated electrosurgical instruments of interest.
It is also noted that some commercially available hand-actuated electrosurgical switching instruments utilize a flexible resilient sheath member externally around the housing and positioned to cover the switching buttons in an attempt to seal the switching mechanism from fluids. While this may keep fluids from entering through the cracks surrounding the actuating buttons, it does not prevent fluids from entering the housing via the cracks at the distal end of the instrument where the electrode blade enters the housing, or at the proximal end where the cable exits from the handpiece. Consequently, this means of sealing is generally not very effective.
Other commercially available hand-actuated electrosurgical switching instruments utilize several strategically placed "O"-rings, placed internally in the housing about the switching areas, relying on several seal points, in order to seal the switching mechanism from fluids.